Retrograde plunger delivery system

ABSTRACT

Cannulas are provided for delivering therapeutic material to a treatment site. The cannula includes a cannula body with a plurality of openings at the distal end, including a longitudinal opening and a plurality of transverse openings that are axially spaced from each other. The cannula also includes a plunger that is configured to be slidably disposed within the cannula lumen. When the plunger is proximally displaced in the cannula lumen, the plunger seals the distal end and deflects the therapeutic material out the transverse openings. As the plunger is proximally displaced within the lumen, the therapeutic material is forced to perfuse out transverse openings located proximal of the plunger position. In one embodiment, the plunger includes an additional pliable sealable member. In another embodiment, the distal end of the cannula body may be implanted by separating the distal end from the cannula body.

FIELD OF THE INVENTION

[0001] This invention relates to medical delivery devices, and inparticular, to cannula needle or sheath systems for directed delivery ofbiomaterials.

BACKGROUND

[0002] Numerous bone conditions or spinal injury can cause painfulcollapse of vertebral bodies, including osteopenia (osteoporosis),vertebral hemangiomas, multiple myeloma, necorotic lesions (Kummel'sDisease, Avascular Necrosis), metastatic disease and complications fromsteroid and non-steroidal anti-inflammatory drug (NSAID) use.Osteoporosis is a systemic, progressive and chronic disease that isusually characterized by low bone mineral density, deterioration of bonyarchitecture, and reduced overall bone strength. FIG. 1A depicts thelateral view of typical spinal motion segments 20, with lumbar vertebrae22, 26, and 28. In contrast, FIG. 1B illustrates a lateral view of asegment of a spinal column that has undergone a vertebral bodycompression fracture (VCF), as shown by the compressed middle vertebra26′. VCFs are more common in people who suffer from these medicalindications, often resulting in pain, compromises to activities of dailyliving, and even prolonged disability.

[0003] Degenerative and injured spinal disk rehabilitation(pharmacological or gene therapeutic) protocols that delay theprogression of intradiscal diseases, or even restore disk health anddisk functions, are a part of contemporary research developments andemerging standards of care. The science of spinal intervention has madegreat strides in recent years. On some occasions, spinal or poly-traumapatients experience VCFs that may be repaired by vertebroplasty andother spinal reconstructive means. Vertebroplasty, which literally meansfixing the vertebral body, has been used in the United States since themid-1990s to treat pain and progressive deterioration associated withVCF. Most often in this vertebroplasty procedure, a bone cement, likeopacified polymethylmethacrylate (PMMA), or other suitable biomaterialalternatives or combinations, is injected percutaneously into the bonyarchitecture under radiographic guidance and controls. The hardening(polymerization) of the cement media or the mechanical interlocking ofother biomaterials serves to buttress the bony vault of the vertebralbody, providing both increased structural integrity and decreasedpotential for painful micromotion and progressive collapse of thevertebrae and spinal column.

[0004] Bone tamps (bone balloons or Kyphoplasty™), a contemporaryballoon-assisted vertebroplasty alternative for treatment of VCF, alsoinvolves injection of a bone cement into a mechanically created bonevoid within vertebral body. In this alternative vertebroplastyprocedure, a balloon tamp is first inserted into the structurallycompromised vertebral body, often through a cannula. The bone balloon isthen inflated under high pressure. It is claimed that the expandingballoon disrupts the cancellous bone architecture and physiologicalmatrix circumferentially and directs the attendant bony debris andphysiologic matrix toward the inner cortex of the vertebral body vault.The balloon tamp is then deflated and removed, leaving a bony void orcavity. The remaining void or cavity is repaired by filling it with anappropriate biomaterial media, most often bone cement. In most cases,the treatment goals are to reduce or eliminate pain and the risk ofprogressive fracture of the vertebral body and its likely resultingmorbidity, complications, and disability.

[0005] Although most of these interventional procedures are animprovement over previous conservative treatments that consisted of bedrest, pharmaceuticals, and/or cumbersome back braces, these methodsstill suffer from practical difficulties associated with filling therelevant anatomy with the therapeutic material. The precise directionand placement of the therapeutic media is fundamental to optimal patientoutcomes. Iatrogenic injury may be reduced or eliminated by the properapplication of a delivery technology. In the case of a damaged vertebralbody, it is usually imperative that the injected therapeutic materials,e.g., bone cement, sufficiently fill the distal (anterior) end of thevertebral body since this is where the diseased tissue is normallylocated. When the delivery device enters the vertebral body from thedistal end, the distal opening of the delivery device is often quicklyencased and clogged with the therapeutic material. And when the deliverydevice is positioned proximal of the target site, however, the fillingof the cavity is often compromised at the distal end.

[0006] Accordingly, it would be desirable to provide treatment systemsand methods that allow for improved delivery of therapeutic material inthe target treatment site.

SUMMARY OF THE INVENTION

[0007] The present inventions are directed to a cannula and methods thatcan be used to deliver therapeutic material to a treatment site in aretrograde manner. Preferably, the inventive cannula is utilized todeliver therapeutic material to bone tissue, such as, e.g., vertebralbodies with compression fractures, but it may also be used at any sitein a human or animal that requires the delivery of therapeutic material.

[0008] In accordance with a first aspect of the present inventions, theinventive cannula includes a cannula body with a plurality of openingsat the distal end that are in fluid communication with a lumen of thecannula body. By way of non-limiting example, the plurality of openingscan include a longitudinal opening disposed at the distal tip of thecannula body and one or more transverse openings located proximal to thedistal tip. If a plurality of transverse openings are provided, they canbe circumferentially offset from each other. The transverse openings canalso be arranged into axially spaced groups of transverse openings. Thecannula also includes a plunger that is configured to be slidablydisposed within a lumen of the cannula body.

[0009] Although the present invention should not necessarily be limitedby this advantage, the presence of a plurality of openings at the distalend of the cannula body and the plunger provide a means to deliver thetherapeutic material to both the proximal and distal ends of thetreatment site without having to proximally displace the whole cannula.If there are multiple transverse openings that are circumferentiallyoffset, even perfusion of the therapeutic material is facilitated. In apreferred embodiment, the plunger may include an additional pliablesealable member that provides a tighter seal between the plunger and theinner wall of the cannula body, thereby ensuring or at least minimizingleakage of the therapeutic material between the plunger and the innerwall.

[0010] In accordance with a second aspect of the present inventions, amethod for delivering implant material into tissue using a cannula isperformed. The cannula comprises a cannula body having first and secondopenings, and a plunger slidably disposed within a lumen of the cannulabody. The method comprises inserting the cannula body into a distalsection of a tissue, and distally displacing the plunger into a firstposition distal to the first opening. The implant material is thenperfused out of the first opening into the tissue. The plunger isproximally displaced into a second position between the first and secondopenings, and the implant material is then perfused out of the secondopening into the tissue while the plunger is in the second position. Byway of non-limiting example, the implant material can be longitudinallyperfused out of the first opening, and transversely perfused out of thesecond opening. This process can be continued if there are anyadditional openings that are proximal to the second opening. Althoughthe present invention should not necessarily be limited by thisadvantage, this inventive delivery method provides for a more desirableplume shape of the therapeutic material. Optionally, the distal portionmay be separated from the proximal portion of the cannula member, e.g.,when the distal tip becomes stuck in the treatment site and it wouldcause the patient harm if it were to be removed.

[0011] In accordance with a third aspect of the invention, the cannulabody includes a detachable structure that allows the distal end of thecannula body to be separated from the proximal end. By way ofnon-limiting example, the detachment structure may include one or moreaxially spaced notches that allow the cannula body to break intomultiple pieces when a shearing force is applied. In a preferredembodiment, the cannula body has a plurality of such notches.Alternatively, the detachment structure may comprise a mechanicaljunction that would allow the cannula body to separate into multiplepieces when an external force is applied. The mechanical junction maycomprise a connective sleeve that detaches into multiple pieces when ashearing or twisting force is applied. In a preferred embodiment, theconnective sleeve may contain holes or recessions to aid in thedetachment. The mechanical junction may also comprises a threadedjunction, wherein the proximal end may be unscrewed from the distalsection end. Although the present invention should not necessarily be solimited, the provision of the detachable structure may be desirable whenthe distal tip becomes stuck in the treatment site and it would causethe patient harm if it were to be removed.

[0012] In accordance with a fourth aspect of the invention, a method fordelivering implant material into tissue using a cannula is performed.The cannula comprises a cannula body having one or more openings. Themethod comprises inserting the cannula body into a distal section of atissue, perfusing the implant material out of the opening into thetissue, and separating the distal end body from the proximal end of thecannula. By way of non-limiting examples, the proximal end is separatedfrom the distal end of the cannula body by detaching the cannula bodyusing a shearing or twisting force or unscrewing the proximal end fromthe distal end.

[0013] Although the present invention should not necessarily be limitedby this advantage, this inventive delivery device provides a means forremoving the delivery device from the treatment site without furtherharming the patient if, e.g., the distal tip is intended for implantatonor becomes embedded in the treatment site and its removal may poseunnecessary patient risk or threaten patient outcomes if removed.

BRIEF DESCRIPTION OF THE FIGURES

[0014] The drawings illustrate the design and utility of preferredembodiments of the present invention, in which similar elements arereferred to by common reference numerals. In order to better appreciatehow the above-recited and other advantages and objects of the presentinventions are obtained, a more particular description of the presentinventions briefly described above will be rendered by reference tospecific embodiments thereof, which are illustrated in the accompanyingdrawings. Understanding that these drawings depict only typicalembodiments of the invention and are not, therefore, to be consideredlimiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

[0015]FIG. 1A shows a lateral view of three normal vertebrae;

[0016]FIG. 1B shows a lateral view of three vertebrae, wherein thevertebral body of the middle vertebra is compressed;

[0017]FIG. 2A shows a side view of a delivery assembly constructed inaccordance with a preferred embodiment of the present inventions;

[0018]FIG. 2B shows a cross-sectional view of the delivery assembly ofFIG. 2A;

[0019]FIG. 3 shows a side view of a delivery assembly constructed inaccordance with another preferred embodiment of the present inventions;

[0020]FIG. 4 shows a side view of a delivery assembly constructed inaccordance with another preferred embodiment of the present inventions;

[0021] FIGS. 5A-5C show side views of delivery assemblies constructed inaccordance with a preferred embodiment of the present invention withdifferent detachment technologies;

[0022]FIG. 6 shows a partially cut-away top view of a lumbar vertebra;

[0023]FIG. 7A shows a lateral view of one posterior access route to theanterior vertebral body shown in FIG. 6;

[0024]FIG. 7B shows a top view of transpedicular and parapedicularroutes to the anterior vertebral body shown in FIG. 6;

[0025] FIGS. 8A-8C shows a side elevational view of the cannula of FIG.2 inserted into a vertebral body; and

[0026]FIG. 8D shows a side elevational view of a severed cannula of FIG.8A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Referring to FIG. 2, a cannula 100 constructed in accordance withone preferred embodiment is illustrated. The cannula 100 generallyincludes a cannula body 108 with an associated slidable plunger assembly105.

[0028] The cannula body 108 has a proximal end 110, a distal end 112,and a lumen 114 extending therethrough between the proximal and distalends 110 and 112. In a preferred embodiment, the distal end 112 of thecannula body 108 is fenestrated. Specifically, the distal end 112 has aplurality of openings including a longitudinal opening 116 at the distaltip 113 of the cannula body 108 and a plurality of axially spacedtransverse openings 118 proximal to the distal tip 113. The longitudinalopening 116 and the plurality of transverse openings 118 are in fluidcommunication with the lumen 114 of the cannula body 108. As illustratedin FIGS. 2A and 2B, the transverse openings 118 are arranged in axiallyspaced groups of openings 118(a)-(e). Each of the transverse openinggroups 118(a)-(e) contains two axially aligned openings 118 that arecircumferentially offset from each other by 180°. Each successivetransverse opening group is circumferentially offset from adjacentgroups by 90°. Alternatively, as illustrated in FIG. 3, each of thetransverse opening groups 118(a)-(e) has four axially aligned openings118 circumferentially offset 90° from each other. Although four openings118 are herein illustrated, the transverse opening groups 118(a)-(e) maycontain any number of openings, such as three axially aligned holescircumferentially offset 60° from each other. Optionally, as illustratedin FIG. 4, the transverse openings are not axially grouped together, butrather each opening 118 is axially and circumferentially offset fromeach other. For example, successive transverse openings 118(a) and (b)are circumferentially offset from each other by 90°. Although an offsetof 90° is herein illustrated, offsets of other angular variations, suchas 60°, may also be used.

[0029] Preferably, the transverse openings 118 extend proximally up thecannula body 108 for a distance approximately equal to the length of thetreatment site. In the case of a vertebral body, the openings 118 mayoccur periodically for approximately 20 mm up from the distal tip 113.The location of the openings 118 around the circumference of the cannulabody 108 in all of these embodiments allow for the therapeutic materialto be perfused 360° around the cannula body 108, thereby filling thetreatment site in a more even manner. Embodiments in which the openings118 are not located circumferentially around the cannula body 108 canalso be made where it is desired to direct the implant material in amore planar treatment site.

[0030] As illustrated in FIGS. 2-4, the transverse openings 118 arerectangular in shape. Transverse openings with different shapes, e.g.,circular or elliptical, may also be used. The side walls of thetransverse openings 118 may also be curved or otherwise shaped todecrease the likelihood that they will become clogged with therapeuticmaterial during delivery.

[0031] The materials used in constructing the cannula body 108 maycomprise any of a wide variety of biocompatible materials. In apreferred embodiment, a radiopaque material such as a metal (e.g.,stainless steel, titanium alloys, or cobalt alloys) or a polymer (e.g.,ultra high molecular weight polyethylene) may be used, as is well knownin the art. In another preferred embodiment, where it is desirable toleave a portion of the cannula body 108 implanted in the patient, abioabsorbable material may be used. These include, but are not limitedto, polylactic acid (PLA) and polyglycolic acid (PGA). Alternatively, abiocompatible material, such as polymethylmethacrylate (PMMA) may beused to form the distal tip 113 of the cannula body 108. A combinationof materials may also be used. For example, a bioabsorbable material(e.g., PLA) may be used to make the distal end 112 and a metal (e.g.,stainless steel) may be used at the proximal end 110.

[0032] The plunger assembly 105 includes a plunger 106 and a moveablemember 136. The plunger 106 has a proximal end 130 and a distal end 132and is configured to be slidably received into the lumen 114 of thecannula body 108. As illustrated in FIG. 2, at position P1, the plunger106 is located distal to the longitudinal opening 116, allowing forlongitudinal and transverse openings 116 and 118 to be in fluidcommunication with the lumen 114 of the cannula body 108. When theplunger 106 is fully received inside the lumen 114 at position P2,located between the longitudinal opening 116 and transverse openinggroup 118(a), the plunger 106 substantially seals longitudinal opening116 so that it is no longer in fluid communication with the lumen 114.As a result, a substantial amount of the fluid or viscous materialcontained within the lumen 114 is deflected from the proximal end 130 ofthe plunger 106 and is forced to perfuse out of transverse openinggroups 118(a)-(e) located proximal to position P2. As the plunger 106 isproximally located at positions P3-P7, transverse opening groups118(b)-(e), respectively, are sealed off such that they are no longer influid communication with lumen 114. For example, when the plunger is atposition P4, the plunger 106 substantially seals off longitudinalopening 116 and transverse opening groups 118(a)-(b), forcing thetherapeutic material to exit through transverse opening groups118(c)-(e). The plunger 106 may be made out of the same biocompatiblematerials used to make the cannula body 108, including any appropriatemetal or polymer or any biocompatible material, such as PLA or PGA.

[0033] The moveable member 136 is attached to the plunger 106 and issubstantially disposed within the lumen 114 of the cannula body 108,allowing for the user to longitudinally displace the plunger 106 withinthe lumen 114. The moveable member 136 is preferably flexible, allowingit to conform to any curves in the cannula body 108 without breaking. Itmay be made from the same materials used to make the cannula body 108,such as PLA or PGA. Alternatively, the moveable member 136 may be madefrom a cable or braided material, such as Titanium. The proximal end ofthe moveable member 136 may be attached to any appropriate means, e.g.mechanical or electrical, to aid in proximally displacing the plunger106. Alternatively, the plunger may be manually displaced. The type ofmaterial selected for the moveable member 136 will depend on theviscosity of the therapeutic material to be implanted. A highly viscousmaterial, such as some bone cements, may require a moveable member witha high tensile strength, such as braided titanium.

[0034] Optionally, the plunger assembly 105 includes an additionalpliable sealing member 134 attached to the proximal end 130 of theplunger 106. In its uncompressed state, the diameter of the additionalpliable sealing member 134 is slightly larger than the diameter of thelumen 114 of the cannula body 108. Therefore, when the plunger 106 andadditional pliable sealing member 134 are slidably received into thelumen 114, the inner wall 115 of the cannula body 108 will compress theadditional pliable sealing member 134 a sufficient distance to permitpassage of the plunger 106 and additional pliable sealing member 134within the lumen 114, while sealing the member 134 against the innerwall 115. Therefore, the additional pliable sealing member 134 willprovide an improved seal, ensuring that any openings 118 located distalto the plunger 106 position are no longer in fluid communication withthe lumen 114. The additional sealing member 134 can be made from anelastopolymer such as “implantable” Ultra-High Molecular WeightPolyethylene (UHMWPE) and silicone, or alternatively, from a shapeablemetal, such as nitinol.

[0035] Optionally, the cannula 100 may include a detachment structure125 that enables the distal end 112 to be separated from the proximalend 110 where desired, or alternatively, where the distal end 112becomes stuck and cannot be retrieved without harming the patient. Wherethe distal end 112 is separated, the distal end 112 of the cannula 100is preferably made from an implantable-grade biomaterial, such as aregulatorily-approved stainless steel, polymer, or ceramic. In apreferred embodiment, as illustrated in FIG. 5A, the cannula 100comprises detachment structure 125(1) that includes a series of axiallyspaced notches 126 in the wall of the cannula body 108, thereby allowingthe cannula body 108 to break into two or more pieces in the presence ofa shearing force. Each notch 126 extends radially inwardly from theexterior of the cannula body 108 to just short of the inner wall 115 ofthe cannula body 108. As with the transverse openings 118 illustrated inFIG. 4, each consecutive notch 126 may be circumferentially offsetrelative to adjacent notches. For example, successive transverse notches126 are offset from each other by 90° . Although an offset of 90° isillustrated in this embodiment, circumferential offsets using otherangular variations may also be used, such as 60°. Alternatively, thenotches 126 can be grouped into axially aligned notches, much like thetransverse opening groups 118 shown in FIGS. 2 and 3. For example, foreach group, two axially aligned notches 118 can be circumferentiallyoffset by 180° (not shown). It should be noted that the number ofnotches 126 illustrated is only meant to be an example; a greater orsmaller number notches 126 may be provided.

[0036] Alternatively, as illustrated in FIG. 5B, the cannula 100comprises detachment structure 125(2) that includes a mechanicaljunction. For example, the distal end 112 could be attached to theproximal end 110 of the cannula body 108 with a threaded junction 127.Where implantation of the distal tip 113 is desired, the proximal end110 could be unscrewed from the distal end 112 using a twisting force.

[0037] In another preferred embodiment, as illustrated in FIG. 5C, thecannula 100 comprises detachment structure 125(3) that includes aconnective sleeve 128 that couples the proximal and distal ends 110 and112. The connective sleeve 128 is preferably thin and may be made out ofplastic, metal, or other appropriate material. Optionally, theconnective sleeve 128 may include holes or recessions 129 to provide aweakened section. Where implantation of the distal tip 113 is desired,an external force, e.g., a shearing or twisting force, could be appliedto the connective sleeve 128.

[0038] Although, as noted above, use of the cannula 100 of the presentinvention is not limited to treatment of vertebral ailments, suchprocedures are discussed here for exemplary purposes. Before discussingsuch methods of operation, various portions of the vertebra are brieflydiscussed. FIG. 6 depicts a top view of a vertebra 50. The posterior ofthe vertebra 50 includes right and left transverse processes 52R, 52L,right and left superior articular processes 54R, 54L, and a spinousprocess 56. The vertebra 50 further includes a centrally located lamina58 with right and left lamina 58R, 58L, that lie in between the spinousprocess 56 and the superior articular processes 54R, 54L, respectively.Right and left pedicles, 60R, 60L, are positioned anterior to the rightand left transverse process, 52R, 52L, respectively. A vertebral arch 61extends between the pedicles 60 and through the lamina 58. The anteriorof the vertebra 50 includes a vertebral body 62, which joins thevertebral arch 61 at the pedicles 60. The vertebral body 62 includes aninterior volume of reticulated, cancellous bone 64 enclosed by acompact, cortical bone 66 around the exterior. The vertebral arch 61 andbody 62 make up the spinal canal, i.e., the vertebral foramen 68; theopening through which the spinal cord and epidural veins pass.

[0039] The physician can choose from a variety of approaches to insertthe cannula 100 into the vertebral body 62. As depicted in FIG. 7A, inthe transpedicular approach, access to the cancellous bone in thevertebral body 62 is gained through the pedicle 60. Alternatively, asdepicted in FIG. 7B, a parapedicular approach 72 may be used in whichaccess is gained through the side of the vertebral body 62 beside thepedicle 60. This approach may be selected if the compression fracturehas resulted in collapse of the vertebral body 62 below the plane of thepedicle 60. Still other physicians may opt for an intercostal approachthrough the ribs (not shown) or a more clinically challenging anteriorapproach (not shown) to the vertebral body 62.

[0040] Referring now to FIGS. 8A-8D, an exemplary procedure for treatinga fractured vertebra 50 using the cannula 100 will be discussed. Turningspecifically to FIG. 8A, a transpedicular approach is used to gainaccess to the interior of the vertebral body 62 through a naturallyoccurring bore or passage 67 in the vertebra 50 formed as a result ofthe condition to be treated. Alternatively, a bore or passage 67 in thebone may be formed with a drill. The size of the bore or passage 67 intothe interior of the vertebral body 62 should be slightly larger than theexternal diameter of the cannula body 108 so that it can be insertedthrough the bore or passage 67 into the vertebral body 62. In addition,the physician may further create a cavity 69 within the vertebral body62 before insertion of the cannula body 108 if desired. This may beaccomplished using any surgical tool to carve out a cavity or perhaps byusing an additional expandable or deployable device, such as those usedin angioplasty or atraumatic tissue expansion or dissection.

[0041] The distal end 112 of the cannula body 108 is preferably placedin the center of the anterior vertebral body void or vault 62, with theplunger 106 positioned distal of the longitudinal opening 116. Once thecannula body 108 is properly placed and the fluid or viscous materialhas been introduced into the lumen 114, the physician may then applysome form of pressure, e.g., a syringe or power device, to force thematerial out the longitudinal and transverse openings 116 and 118 at thedistal end 112. As illustrated in FIG. 8A, when the plunger 106 is atposition P1 (shown in FIG. 2), the majority of the fluid or viscousmaterial will perfuse out the longitudinal opening 116, although somewill also perfuse out the transverse openings 118.

[0042] Referring now to FIG. 8B, the physician can then proximallydisplace the plunger 106 by retracting the attached moveable member 136,either by manual, mechanical, or electrical means. As the plunger 106 isproximally displaced into the lumen 114 to a position P2 (shown in FIG.2) between the longitudinal opening 116 and the distal-most transverseopening group 118(a), the plunger 106 substantially seals off thelongitudinal opening 116, thereby forcing the fluid or viscous materialto perfuse through the transverse opening groups 118(a)-(e). As thedistal portion of the treatment site is filled, the plunger 106 canagain be proximally displaced to a new position P3 (shown in FIG. 2)between transverse opening groups 118(a) and (b), thereby substantiallysealing off the longitudinal opening 116 and transverse opening group118(a). This forces the implant material to perfuse out transverseopenings located proximal of transverse opening group 118(a), i.e.,transverse opening groups 118(b)-(e). As illustrated in FIGS. 8C-8D, theprocess of proximally displacing the plunger 106 to positions P4-P7 canbe repeated until the therapeutic site is filled as desired. Bysequentially forcing the implant material out of the transverse openings118, a more even distribution of the implant material in the treatmentsite results without having to proximally displace the entire cannulabody 108. Where a bone cement is delivered to a vertebral body 62, thisdelivery technique results in a more desirable cloud-like plume shape 70of the bone cement, which provides increased structural integrity forthe damaged vertebra. Although the implant material has been describedas being delivered within the vertebra 50 using the cannula 100illustrated in FIG. 2A, other cannulae, such as those illustrated inFIGS. 3 and 4 can be used as well.

[0043] Where implantation of the distal end 112 of the cannula body 108is desired, or where it cannot be removed without harming the patient,the distal end 112 can be separated or severed from the proximal end 110and left in the vertebra 50. As illustrated in FIG. 8D, the physician,with the aid of well known visualization and imaging techniques, mayslip outer tube 102 over the exposed proximal end 110 of the cannulabody 108 until the free end of the outer tube 102 is aligned with thefirst notch 126 external to the vertebra. The cannula body 108 can thenbe severed by applying a shearing force, urging the proximal end 110laterally in the direction that tends to separate the selected notch128. Alternatively, the distal end 112 may be severed by applying anexternal twisting force, depending on the design of the cannula body108. The proximal end 110 of the cannula body 108 can then by extractedfrom the patient. Any of the other detachment structures 125 can be usedas well to separate the distal and proximal ends 112 and 110.

[0044] Although particular embodiments of the present inventions havebeen shown and described, it will be understood that it is not intendedto limit the present inventions to the preferred embodiments, and itwill be obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed:
 1. A cannula for use in delivering therapeuticmaterial, comprising: a cannula body having a proximal end, a distalend, and a lumen extending between the proximal and distal ends, whereinthe distal end of the cannula body includes a plurality of openingsaxially spaced from each other in fluid communication with the lumen;and a plunger configured to be slidably disposed within the lumen. 2.The cannula of claim 1, further comprising a detachment structure thatallows the distal end to be separated from the proximal end of thecannula body.
 3. The cannula of claim 2, wherein the detachmentstructure comprises one or more axially spaced notches that allows thecannula body to break into two or more pieces in the presence of ashearing or twisting force.
 4. The cannula of claim 3, wherein the oneor more notches comprises a plurality of notches.
 5. The cannula ofclaim 3, wherein the one or more notches are circumferentially offsetfrom each other.
 6. The cannula of claim 2, wherein the detachmentstructure comprises a mechanical junction that allows the cannula bodyto separate into two pieces in the presence of an external force.
 7. Thecannula of claim 6, wherein the mechanical junction comprises aconnective sleeve that allows the cannula body to separate into twopieces in the presence of the external force.
 8. The cannula of claim 6,wherein the mechanical junction comprises a threaded junction thatallows the cannula body to separate into two pieces in the presence of arotational force.
 9. The cannula of claim 1, wherein the plunger furthercomprises a pliable sealing member.
 10. The cannula of claim 1, whereinthe cannula body comprises a biocompatible material.
 11. The cannula ofclaim 1, wherein the plunger comprises a biocompatible material.
 12. Thecannula of claim 1, wherein the plurality of openings comprises alongitudinal opening at a distal tip of the cannula body, and atransverse opening proximal to the distal tip of the cannula body. 13.The cannula of claim 1, wherein the plurality of openings furthercomprises a plurality of axially spaced transverse openings proximal tothe distal tip of the cannula body.
 14. The cannula of claim 13, whereinthe plurality of transverse openings are circumferentially offset fromeach other.
 15. The cannula of claim 13, wherein the plurality oftransverse openings is arranged into axially spaced groups.
 16. Thecannula of claim 15, wherein each transverse opening group comprises aplurality of axially aligned openings.
 17. A method for deliveringimplant material into tissue using a cannula comprising a cannula bodyhaving a first opening and a second opening proximal to the firstopening, and a plunger slidably disposed within a lumen of the cannulabody, the method comprising: inserting the cannula body into a distalsection of a tissue; perfusing the implant material out of the firstopening into the tissue; proximally displacing the plunger from a firstposition distal to the first opening into a second position between thefirst and second openings; and perfusing the implant material out of thesecond opening into the tissue while the plunger is in the secondposition.
 18. The method of claim 17, further comprising severing adistal portion from a proximal portion of the cannula member.
 19. Themethod of claim 17, further comprising separating a distal portion froma proximal portion of the cannula member.
 20. The method of claim 17,wherein the implant material is longitudinally perfused out of thecannula body through the first opening, and transversely perfused out ofthe cannula body through the second opening.
 21. The method of claim 17,wherein the cannula body further comprises a third opening proximal tothe second opening, the method further comprising: proximally displacingthe plunger into a third position between the second and third openings;and perfusing the implant material out of the third opening into thetissue while the plunger is in the third position.
 22. The method ofclaim 12, wherein the implantable material is bone cement.
 23. Themethod of claim 17, wherein the tissue is bone tissue.
 24. The method ofclaim 23, wherein the bone tissue is a vertebral body.
 25. A cannula foruse in delivering therapeutic material, comprising: a cannula bodyhaving a proximal end, a distal end, a lumen extending between theproximal and distal end, and a detachment structure that allows thedistal end to be separated from the proximal end.
 26. The cannula ofclaim 25, wherein the detachment structure comprises one or more axiallyspaced notches that allows the cannula body to detach into two or morepieces in the presence of a shearing or twisting force.
 27. The cannulaof claim 26, wherein the one or more notches comprises a plurality ofnotches.
 28. The cannula of claim 26, wherein the one or more notchesare circumferentially offset from each other.
 29. The cannula of claim25, wherein the detachment structure comprises a mechanical junctionthat allows the cannula body to separate into two pieces in the presenceof an external force.
 30. The cannula of claim 29, wherein themechanical junction comprises a connective sleeve that allows thecannula body to separate into two pieces in the presence of the externalforce.
 31. The cannula of claim 29, wherein the mechanical junctioncomprises a threaded junction that allows the cannula body to separateinto two pieces in the presence of a rotational force.
 32. The cannulaof claim 25, wherein the cannula body comprises a bioabsorbablematerial.
 33. The cannula of claim 25, wherein the cannula body furthercomprises a plurality of openings axially spaced from each other influid communication with the lumen.
 34. The cannula of claim 33, whereinthe opening comprises a longitudinal opening at a distal tip of thecannula body and the plurality of openings comprise at least onetransverse opening proximal to the distal tip of the cannula body. 35.The cannula of claim 34, wherein the plurality of transverse openingsare circumferentially offset from each other.
 36. The cannula of claim34, wherein the plurality of transverse openings is arranged intoaxially spaced groups.
 37. The cannula of claim 34, wherein eachtransverse opening group comprises a plurality of axially alignedopenings.
 38. A method for delivering implant material into tissue usinga cannula comprising a cannula body having a proximal end, a distal end,one or more openings, the method comprising: inserting the cannula bodyinto tissue; perfusing the implant material out of the one or moreopenings into the tissue; and separating the proximal end from thedistal end of the cannula body.
 39. The method of claim 38, wherein theimplantable material is bone cement.
 40. The method of claim 38, whereinthe tissue is bone tissue.
 41. The method of claim 40, wherein the bonetissue is a vertebral body.
 42. The method of claim 38, wherein the oneor more openings comprises a plurality of openings axially spaced fromeach other the method further comprising perfusing the implant materialout of the plurality of openings into the tissue.
 43. The method ofclaim 38, wherein the cannula further comprises a plunger configured tobe slidably disposed in a lumen of the cannula body, and the one or moreopenings comprises a first opening and a second opening proximal to thefirst opening, the method further comprising: proximally displacing theplunger from a first position distal to the first opening into a secondposition between the first and second openings; and perfusing theimplant material out of the second opening into the tissue while theplunger is in the second position.
 44. The method of claim 38, whereinseparating the proximal end from the distal end of the cannula bodycomprises detaching the cannula body by applying a shearing or twistingforce.
 45. The method of claim 38, wherein separating the proximal endfrom the distal end of the cannula body comprises unscrewing theproximal end from the distal end.
 46. The method of claim 38, furthercomprising implanting the distal end of the cannula body within thetissue.
 47. The method of claim 46, wherein the distal end of thecannula body is composed of a biocompatible material.